A group of researchers at MIT has developed a wireless underwater camera that works without batteries. The device converts sound into electrical energy. It is about 100,000 times more energy efficient than other underwater cameras.
The underwater camera devised by MIT engineers does not require cables or batteries, works with sound and takes color photographs, even in the darkness of the depths. In addition, it is about 100,000 times more energy efficient than other underwater cameras.
Exploring unknown regions of the ocean is no easy task. So much so that it is estimated that we have not observed more than 95% of the Earth’s oceans, that is, we know less about the oceans of our planet than about the far side of the Moon or the surface of Mars.
Part of the blame for this ignorance is that having an underwater camera running for a long time is very expensive. It has to be tied to a research vessel or sent to a ship to recharge its batteries. Well, the new wireless underwater camera that does not need batteries could change things.
The autonomous camera works with sound. It converts the mechanical energy of sound waves traveling through water into electrical energy that powers your imaging and communications equipment. After capturing and encoding the image data, the camera also uses the sound waves to transmit the data to a receiver that reconstructs the image.
Since it doesn’t need a power source, the camera could be running for weeks, allowing scientists to search for new species in remote areas of the ocean, capture images of ocean pollution or monitor the health and growth of aquaculture-raised fish.
“One of the most interesting applications of this camera for me personally is in the context of climate monitoring. We are building climate models, but we lack data on more than 95% of the ocean. This technology could help us build more accurate climate models and better understand the impact of climate change on the underwater world,” said Fadel Adib, associate professor in the Department of Electrical and Computer Engineering and chair of the Signal Kinetics group at MIT’s Media Lab, and senior author of the paper.
How sound is converted into electrical energy
In order for the camera to be autonomous for long periods of time, the researchers needed it to be able to collect energy itself while in the water and consume little.
The camera takes the energy through transducers placed on the outside that are made of piezoelectric materials. These materials produce an electrical signal when a mechanical force is applied to them. In this way, when a sound wave traveling through the water collides with the transducers, they vibrate and convert that mechanical energy into electrical energy.
The sound waves can come from marine life itself or from a passing ship. The camera stores the energy it has harvested until it accumulates enough to power the electronic components responsible for taking the photos and communicating the data.
To ensure that the camera consumed little, the researchers used very low power image sensors. The problem is that these sensors only capture gray images. In addition, as most underwater areas lack light, they had to develop a flash, also low consumption. They solved both difficulties by using red, green and blue LED lights. When the camera captures an image, it shines a red LED and then uses the image sensors to take the photo. Repeat the same process with green and blue LEDs. Although the image appears black and white, red, green, and blue light is reflected off the white part of each photo. In this way, when the image data is combined in post-processing, it can be reconstructed in color.
Researchers have tested the camera in various underwater environments with satisfactory results. At the New Hampshire pond they captured color photos of plastic bottles that were floating. They also obtained snapshots of such quality of a starfish that the spines of its arms were clearly visible. The device also worked when it was used to make, for a week, photographs of a plant that lives in a dark area to document how it grew.
The next step is to increase the camera’s memory so you can take real-time photos, transmit images, or even record videos underwater. For now, the camera transmits data to a maximum of 40 meters from the receiver. Another goal will be to increase that range so that it can be used in more underwater environments.
Reference: Afzal, S.S., Akbar, W., Rodriguez, O. et al. Battery-free wireless imaging of underwater environments. Nature Communications. (2022). DOI: https://doi.org/10.1038/s41467-022-33223-x